The conventional method of incapacitating a motor cycle is to use a U-shaped lock, which is put through the wheel frame so as to prevent the theft or the unauthorized use of the motor cycle. The use of such U-shaped lock to disable a motor cycle is inconvenient and troublesome, in view of the fact that the position of the wheel to be locked must be first adjusted properly to allow the U-shaped lock to be put through the wheel frame, and that the U-shaped lock is too bulky to be carried on a motor cycle, which is provided with little or no space for holding the U-shaped lock.